Research progress and prospects on the characterization of molecular structure evolution during coal pyrolysis and conversion using high-resolution infrared spectroscopy

This article reviews the progress, challenges, and future trends of infrared spectroscopy in the characterization of coal macromolecular structures. Leveraging its unique properties, infrared spectroscopy enables precise analysis of functional groups in coal, exerting a significant influence on coal combustion, gasification, and pollutant formation mechanisms. When combined with chemometrics, it achieves accurate quantification of functional groups, providing a basis for describing coal molecular structures. Comparing infrared spectra of coals at different ranks reveals quantitative relationships in structural transformations during coalification, facilitating real-time monitoring of structural changes to optimize processing technologies. However, the heterogeneity and complexity of coal samples pose challenges to spectral interpretation. In the future, infrared spectroscopy is expected to make advancements in areas such as high resolution, multidimensional spectroscopy, and intelligent data analysis. In particular, the integration of quantum cascade lasers (QCL), two-dimensional correlation spectroscopy, and deep learning will enhance the ability to explore coal molecular structures. Interdisciplinary collaboration will propel the application of infrared spectroscopy in clean coal conversion and environmental protection, laying the foundation for efficient and low-pollution utilization of coal.